Radioactivity refers to the phenomenon that element spontaneously emanates rays (such as αrays, β rays, γ rays, etc.) from unstable nuclei until it is decayed to form a stable element (decay product). Under the radiation of large doses of rays, the human body and animal will suffer damage to some degree. Radioactivity may damage genetic material, which mainly may lead to genetic mutations and chromosomal aberrations. The effect of radioactive material on the human body is closely related to the dose of radiation. For example, a death rate of the irradiated person is 5% under the irradiation of 400 rad. A death rate of the irradiated person is 100% under the irradiation of 650 rad. A death rate is 0 under the irradiation of less than 150 rad, but the radioactivity under such a dose still injures the human body, while the impact on the human body will not show up until a long time period (for example, 20 years) has passed.
It should be noted that, information disclosed in the above background portion is provided only for better understanding of the background of the present disclosure, and thus it may contain information that does not form the prior art known by those ordinary skilled in the art.